Cloth and smoke simulation not working
Since my comment worked, here it is as an actual answer:

When your collision object has no thickness, you either need to add thickness (e.g. by using solidify), or check the Is Planar box, and fake thickness with the Surface Thicknesss slider. 



A lower value will be more realistic, but risk smoke passing straight through, while higher values will more likely stop the smoke, but might look weird as the smoke will stop before reaching the geometry.